Rat brain capillary thrombomodulin: structure and function

Area of Science:

• Biochemistry
• Vascular Biology
• Neuroscience

Background:

• Transmembrane glycoprotein thrombomodulin (TM) is expressed on endothelial cells and plays an anticoagulant role.
• TM and its mRNA are found in brain microvessels, enabling protein C activation.
• Stroke risk factors impair brain protein C activation by downregulating TM.

Purpose of the Study:

• To investigate the role of TM in brain hemostasis using a rat model.
• To determine the TM sequence in rat brain capillaries and compare it with other species.
• To understand the evolutionary conservation of TM's structure and function.

Main Methods:

• Partial sequencing of TM mRNA from rat brain capillaries.
• Deduction of amino acid sequences for rat TM.
• Comparative analysis of TM sequences across species (rat, mouse, bovine, human).

Main Results:

• High sequence homology (77-100%) between rat and mouse TM, particularly in functional domains like epidermal growth factor repeats (EGFRs) and the transmembrane region.
• Significant homology (92-96% for transmembrane region) observed between rat, bovine, and human TM.
• Conservation of all cysteine residues and key amino acids essential for protein C activation.

Conclusions:

• The highly conserved TM sequences across species suggest a similar anticoagulant function in both brain and systemic vascular endothelial cells.
• Rat TM shares significant structural similarities with TM from other mammals, validating its use as a model for stroke research.
• The findings underscore the fundamental importance of TM in maintaining vascular hemostasis.